Studies of adult rat motoneurones using in vitro slice preparations are rare. We here describe a novel brainstem slice of the adult rat containing the facial motor nucleus (FMN). Data obtained for facial motoneurones (FM) by intracellular recording indicate that they display several passive and active properties seen in other rat cranial and spinal motoneurones. Bath application of serotonin (5-HT) evokes a reversible depolarization of FMs which is associated with an increase in input resistance due to a reduction in potassium permeability. This effect is unaffected by tetrodotoxin indicating a postsynaptic site of action.